You may have noticed the letters and numbers on
the side of your tires. But what exactly does it all mean?

The letters and numbers, correspond to the ratings of your tires. Here
we teach you what it all means, in plain English.

Let's use an example of a tire like P180/55R15 85T to teach you what it
all means. The final 85T is known as the service description of the
tire. This is gonna tell you the tires load index and speed rating.Tire
manufacturers have been required since 1991 to display this information
on the tire.

The service description is important, because it identifies the amount
of weight the tire can carry and the maximum recommended speed of the
tire.

The first two digits of the service description corresponds to the tires
load index. So in the example we take the 87T, 87 represents a load
index of the tire. The higher the number of the low index, the higher
the carrying capacity of the tire. Below is a chart showing load indexes
and their corresponding carrying capacity.

Load Index

Pounds

Kilograms

Load Index

Pounds

Kilograms

71

761

345

91

1356

615

72

783

355

92

1389

630

73

805

365

93

1433

650

74

827

375

94

1477

670

75

853

387

95

1521

690

76

882

400

96

1565

710

77

908

412

97

1609

730

78

937

425

98

1653

750

79

963

437

99

1709

775

80

992

450

100

1764

800

81

1019

462

101

1819

825

82

1047

475

102

1874

850

83

1074

487

103

1929

875

84

1102

500

104

1984

900

85

1135

515

105

2039

925

86

1168

530

106

2094

950

87

1201

545

107

2149

975

88

1235

560

108

2205

1000

89

1279

580

109

2271

1030

90

1323

600

110

2337

1060

The next important number is the speed rating, the
letter after the load index number, gives us the tires speed rating.
Using our example of P180/55R15 85T, the letter T will give us the tire
speed rating. In this case it's 118 mph or 180 kmh, this means that the
tire should never be driven faster than 118 mph. Of course, most
highways won't permit this type of speed anyways.
Below is another chart showing you the letter and corresponding speed
rating for each tire. Z rated tires were originally designed to be the
highest speed rated tires. Z means in excess of 149mph. However the V, W
and Y ratings were later introduced, which further clarify the
capability of these extreme speed tires.